Satellite Communications/Link budget
QUESTION: Good night,
I have a question I need to transmit 3 carriers in 1 HPA
de bandwidth are 20 MHz, 8 MHz and 8 MHz the satellite bandwidth is 36 MHz what change do i have to make in my link Budget calculations?
if I want to transmit the 3 carriers with and 1 HPA ?
also I have a link Budget calculation in SCPC but I want to make the calculations with Carrier in Carrier
what parameters I have to change to make the calculations in Carrier in Carrier¡??
Im looking forward for your answer
ANSWER: Hi Mr Eduardo,
Your problem does not have any thing to do with multi carrier transmission in a
Transponder. All transponders in Satellites carry multiple carriers.
What you need to understand is the design of your HPA for the carriers you want
to uplink and also the respective bandwidths each carrier is occupying. The HPAs
in Earth stations are supposed to be operational for the total Satellite capacity
irrespective of the transponder number and bandwidth. some of the sub-carriers may
be in one transponder and the others may be in another , however they need to be
defined for specific applications and the link budget is estimated based on the
requirement of Power and bandwidth.
Your requirement calls for total 36 MHz of satellite transponder space with
differing bandwidths for each carrier. You calculate each carrier link margin
based on the modulation techniques and establish correct link. Then you have to
design your HPA with sufficient back off to take care of linear performance in
the HPA for multi carrier operation.
I am not sure what you may be meaning by carrier in carrier operation. The scheme
is basically called multi carrier operation in the HPA with full bandwidth linear
You can use one HPA with any number of carriers, not just three, if you have
sufficient Back off margin.Cheers/GTRao
---------- FOLLOW-UP ----------
QUESTION: Thank you but when you transmit with multi Carrier you dont need to change the OBO and IBO From the satellite ? To get IBO and OBO per Carrier and it no depends the number of carriers that you are going to transmit??
Carrier in Carrier its when you have 2 satellite link and you transmit and receive with the same frequency in the 2 satellite link
the two Carrier overlap each other in the same frequency
Dear Mr Eduardo,
IBO and OBO are not criterion for your HPA. What I am mentioning is the BO for your HPA for multi carrier operation. If sufficient BO is not available, HPA will be losing efficiency and maximum power will be affected. IBO and OBO are the specifications given by the satellite operator for protection at input and output levels to meet QOS performance. So you need not link these parameters for your applications.
What you need to calculate is for HPA to perform in multi carrier environment ONLY.